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F4 Laars Endurance

Dave99 Member Posts: 1
Laars endurance boiler  (does heat and hot water)

modle EBP

for the last few weeks the hot water has been eratic. It will start hot then drop off in seconds then I would adjust the water hoter at the sink tap or shower and it would ok for about 30 seconds then get very hot and I would have to keep adjusting it though out a shower or doing dishes.

 Yesterday it got very cold, I see a F4 error code. The book said to check the Supply sensor. normal is 10k ohms at 77F  and replace sensor if it reads les then 500 or more then 20k.

Iam getting 14k  but the tank is still warm (about140F).

I check the wires from the sensor to the control and they are fine.

 I have worked on Gas and eletric heaters before but have little experiance with boilers.  Iam thinking I need a new boiler control.

Anyone have any suggestions?



  • Bill H.
    Bill H. Member Posts: 30
    LAARS flow switch


          I had a similar problem. My flow sensor switch was defective. The switch was located inside the unit and above the flat plate heat exchanger. LAARS has a replacement unit that mounts outside the boiler; it operates as a paddle switch, and requires some piping modification. The original seems to be some type of solid state unit and isn't the easiest to replace; ergo the product improvement. You can override your switch by TEMPORARILY removing the wire connections and placing a jumper across them. This should cause the boiler to go into DHW mode and produce a steady volume of hot water. If you still have temperature variation its probably something else. Are your radiators varying  also?
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